Optical elements such as lenses, plain plates, mirrors, prism and others are used in optical imaging devices, for example camera objectives, telescopes or binoculars. Optical elements of this type generally consist of glass and are held on a support device by means of metal or plastic components. To achieve a high imaging quality with optical imaging devices, it is necessary for these holding devices to have a high mechanical stability. If optical imaging devices are exposed to changing environmental influences, such as for example temperature fluctuations, there is a risk of the optical elements of the imaging device in the imaging beam path moving. In the case of imaging devices, this causes color errors and geometric image errors. Errors of this type can also be produced by vibrations and bumps.
To increase the thermal stability of camera objectives, it is known, for example, from EP 0 298 058 B1 to provide an annular, slotted holding element made from aluminum for a lens. Radial recesses are situated at regular intervals at this holding element and have the effect of ensuring that the lens does not shift out of the optical axis of the objective in the event of temperature fluctuations despite the holding element and lens having a different expansion.
Particularly high stability requirements are imposed on objectives for aerial picture cameras. Aerial picture cameras of this type are required to provide a geometrically accurate image of an image area by means of an aerial picture. The picture resolution and the geometric picture stability has to be at least 2 μm over the entire image area. To satisfy these requirements over a wide temperature range from approx. −40° C. to approx. +70° C. and under vibrational and impact loads in flight, objectives of this type are made from metal materials, the expansion coefficient of which is matched to that of the optical glasses used in the objective. For aerial picture camera objectives, such as for example the objective DMC 4/120 mm produced by Carl Zeiss, therefore, the material X14 with a coefficient of thermal expansion α in the range from 10*10−6K−1 to 11*10−6K−1 is used for lens mounts, or alternatively titanium is used, the coefficient of thermal expansion of which is α=9*10−6K−1. The outer housing of an objective of this type is usually made from special steel, for example X14 or X12. This allows the mechanical stresses which the outer housing exerts on the lens mounts to be minimized. However, the materials mentioned are approximately three times as heavy as aluminum. Aluminum is used as material for mounts and housings of conventional photographic objectives. On account of its high coefficient of thermal expansion of α=24*10−6K−1, however, it is not suitable for use in objectives for aerial picture cameras. This would lead to excessive distortion and inadequate imaging performance.